1. Field of the Invention
The present invention relates to a power transmitting apparatus, a power transfer system, and a control method for the power transmitting apparatus.
2. Description of the Related Art
There is known a wireless power transfer system for generating an alternating current in a power transmitting antenna, and transferring the power to a power receiving antenna. Japanese Patent Laid Open No. 2010-051137 discloses that the efficiency becomes high when the resonance frequency of a power transmitting antenna coincides with that of a power receiving antenna, and also discloses a technique of controlling a resonance frequency and detecting a frequency at which power transmission efficiency is high. US-2008-0297107 discloses a technique of controlling the resonance frequency of a power transmitting antenna after detecting a decrease in power transfer efficiency due to a change in relative positional relationship between the power transmitting antenna and a power receiving antenna, thereby preventing the power transfer efficiency from constantly decreasing.